The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingSteering angle sensor zero point malfunction
Description
The skid control ecu learns the steering sensor zero point every time the
ignition switch is turned on and
the vehicle is driven at 35 km/h (22 mph) or more for approximately 5 seconds.
The ecu also stores the
previous zero point.
If front wheel alignment or the steering wh ...
Tire pressure warning ecu
Components
Removal
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove glove compartment door
assembly (see page i ...
Fail-safe chart
Fail-safe chart
This function minimizes the loss of the ect functions
when a malfunction occurs in a sensor or solenoid.
Automatic transmission fluid (atf) temperature
sensor:
when the atf temperature sensor has a
malfunction, o/d up-shift is prohibited
Counter gear speed sensor n ...